Mobile devices (MDs) are an increasingly ubiquitous component of telecommunications infrastructure. MDs can be mobile telephones, laptop computers with a radio link, or other portable devices. MDs, such as mobile telephones, use wireless media to communicate with their respective receivers, typically fixed in geographical position. One type of network protocol used by wireless receivers and by MDs is Internet Protocol (IP). In IP, data is segmented into data packets having known characteristics and formats. IP packets are routed to their intended destinations as a function of the information contained within these packets.
In wireless network, services, such as prepaid voice, instant messaging, broadcasting of information, and so forth, are provided to the MD through devices known as an application server (AS). An AS is a network element controlling applications, wherein the application is some part of a service that requires the use of IP bearer resources. In a wireless system that uses IP as a transport, a service is provided to an MD through the exchange of IP packets with a particular AS. Examples are servers that enable instant messaging, or a P-CSCF (Proxy Call Session Control Function) that provides routing for session initiation protocol (SIP)-based services. Each AS has its own unique IP address, which allows IP packets from a MD to be routed to the AS for the appropriate processing. However, there can be problems associated with this routing of IP packets to an AS.
One problem is if an MD desires a particular type of service the MD must discover the IP address of an AS that can perform functions related to that particular type of service. In general an AS performing a particular application function is associated with an IP network. Thus, if for example the MD is attempting to send an instant message, the AS performing this function in Operator's A network would not necessarily be the same AS performing this function in Operator's B network. Therefore, before attempting to send the instant message, the MD would have to determine the IP address of the AS performing that function in the network presently providing access to IP resources to the MD.
Although there are methods for an MD to obtain an IP address of the AS the methods do not take into consideration the routing restriction placed upon the request, such as either by the operator providing the access to IP resources, or the operator with whom the user has a subscription. Thus, in some scenarios, the MD being provided IP resources in Operator's A network might have the request for the IP address of an AS sent to Operator's B network (for Operator B is the operator for which the user has a subscription with). For these scenarios the response to the request would provide an IP address of an AS in Operator's B network instead of the desired response which would be an IP address of an AS in Operator's A network.
Therefore, there is a need for a mechanism to ensure that the MD requesting the IP address of an AS receives a response that contains an IP address of an AS associated with the network presently providing IP resources to the MD.